the destro line is ok, tho as stated, not especially imaginitive. I would sya, for it to work at higher levels i've really needed to dual cast and use impact perk to do what i can to cause an interupt.
I did the asuras star questline last night and throughout there were some hardass mage mobs that casued me no end of bother. Using impact and dual cast to interupt their actions was essential.
Illusion and alteration i like the most, but are need in conjuntion wioth some damage source...be it destro, a backstabber or archer. conjuration just annoyed me a bit. resto is fairly obviously needed.